christensen



Jan. 3l, 1956 P. M. cHRlsTENsEN 2,733,312 CIRCUIT BREAKER WITH ARC BLOW-OUT Filed Jan. 7, 1950 F1E E 2 Sheets-Sheet 1 FlE- E' INVENTOR. /76 PAI/L M. CHR/STfA/SEA/ H 7 TOR/V575 Jan. 31, 1956 P. M. cHRlsTENsEN 2,733,312

CIRCUIT BREAKER WITH ARC BLOW-OUT Filed Jan. 7, 1950 2 Sheets-Sheet 2 IN VEN TOR. /D/IUA M CHR/STE/VSE/V BY M+ iam United States Patent C) 2,733,312 CIRCUIT BREAKER WITH ARC BLOW-OUT Paul M. Christensen, West Orange, N. J., assignor to Federal Electric Products Company, Newark, N. J., a corporation Application January 7, 1950, Serial No. 137,402

12 Claims. (Cl. 200-87) This invention relates to circuit breakers and more particularly to circuit breakers disposed within enciosures 0r casings therefor.

One object of the invention is to provide an enclosed circuit breaker with means to prevent or minimize damage to or impairment of the circuit breaker mechanism by arcs which may be formed during the operation of the circuit breaker for opening the circuit under load.

Another object is the provision, in an automatic circuit breaker having a casing provided with an arcing chamber which has communication through the casing to the exterior thereof, of means for impelling arcs away from the circuit breaker mechanism and through said chamber to the exterior of said casing.

A further object is the provision of arc blow-out means of generally improved construction and operation.

The above and other objects, features and advantages of the present invention will be more fully understood from the following description considered in connection with the accompanying illustrative drawings.

In the drawings:

Fig. 1 is a side view of a circuit breaker embodying the present invention;

Figs. 2 and 3 are end views as seen from lines 2-2 and 3 3, respectively, of Fig. 1;

Fig. 4 is a side view of the circuit breaker, one part of the casing being removed, the circuit breaker mechanism being open;

Fig. 5 is a view similar to Fig. breaker mechanism closed;

Fig. 6 is a sectional view on the line 6-6 of Fig. 5;

Fig. 7 is a sectional view on the line 7 7 of Fig. 5;

Fig. 8 is a sectional View on the line 8-8 of Fig. 5;

Figs. 9 and 10 are detail views showing dilerent ways 4 showing the circuit of securing the blow-out means to the movable contact arm of the circuit breaker;

Fig. ll is a fragmentary View showing another embodiment of the invention, the circuit breaker mechanism being open;

Fig. 12 s a view similar to Fig. l1, the circuit breaker vmechanism being closed; and

Figs. 13A, 13B, 14A and 14B illustrate, more or less diagrammatically the electrical and magnetic fields existing during the operation of the present invention.

Referring now to Figs. l through 8 of the drawings in detail, the present invention is illustrated and described in connection with an automatic circuit breaker of the type illustrated and described in the application of Thomas M. Cole, Serial No. 127,433, led November l5, 1949, now U. S. Patent 2,647,186 granted July 28, 1953, and assigned to the assignee hereof, but it will be understood that this invention is not limited specifically to the circuit breaker construction of said application. Asgdescribed in said application, and as here shown, the circuit breaker comprises a two part insulation housing or casing formed by body part 12 and the cover or closure part 14, each of said parts being formed of insulation material preferably by a molding operation, and

being secured in housing-defining relation in any suitable way, for example, by bolts 16.

ln the illustrated embodiment of the invention, the circuit breaker is of the plug-in type for use with a terminal plate assembly such as that described in application, Serial No. 127,432 tiled November 15, 1949, now U. S. Patent 2,647,225 granted July 28, 1953, by said Thomas M. Cole and myself, as joint inventors, and assigned to the asignee of my present application. It will be understood, however, that the invention is not limited to the circuit breakers of the plug-in type. As illustrated and described in both applications, above identified, the casing is provided, at one end thereof, with an open recess 18 formed in the body part 12 and adapted to engage a hooked element of the terminal plate assembly and at its other end, the casing is provided with a re-entrant lower portion 20 formed in both the body part 12 and the closure part 14, and adapted to encompass the side and a portion of the top surface of a contact block unit of said terminal plate assembly when mounted thereon. The housing is provided, above said re-entrant portion 20, with a chamber 22. A plug-in terminal prong or stab Contact 24 is mounted vertically in said chamber, said stab contact being adapted for making contact with said terminal block unit and being provided with the laterally extending portions or arms 26 which are removably positioned in cooperating recesses 27 formed in the walls of said chamber, as illustrated and described in said applications.

The casing is provided, above the open recess 18 therein, with an arcing chamber 28 in which the stationary Contact 30 and the movable contact 32 are disposed for relative movement. It will be noted that said arcing chamber is bounded by the similarly thickened portions 34. 36 and 33 ot viali 4t? of the body part, and by the portion 42 of said wall, which extends between the portions 36 and 38, and which is thickened to a lesser extent than said other portions. It will be noted also that p0rtion 38 is provided with a shoulder 44 where it extends above portion 42 and that portion 36 is provided with an angular step 46 where it extends above portion 42. The cover part 14 is provided on its inner surface with a nally of the casing and the guideway opening 54 opposite thereto.

and 58 of wall 40, which also bounds chamber 22, by portions 38, 42 and 48 opposing said portion 60, and by wall 40 and cover 14. It will be noted that guideway 54 extends between chamber 55 and the arcing chamber 28. The edge portion 56 is provided with an o ening 62 therein through which a handle 64 projects for manual operation of the circuit breaker mechanism. The handle is formed of insulation material and is provided with the laterally extending circular pivot portions 65, 65, which are positioned in the bearing recesses 67, 67, respectively, formed in each of the casing parts.

Referring now to the circuit breaker mechanism disposed in chamber :5, as illustrated and described in the rst mentioned application of Thomas M. Cole, an as here shown, said mechanism includes a manually operable member, here shown as the above-mentioned pivoted handle 64. A uni-planar movable contact or switch member 66 is mounted in the chamber 55 for pivotal movement by pivot pin 72, the opposite ends of which are received in the aligned bearing projections 74 on the inner surfaces of each of the casing parts. Said contact member 66 is provided with the contact 32 which is engageable with and disenvageable from the companion stationary Contact 36 carried by the terminal member 76, which will hereinafter be more particularly described. An end portion 78 of the movable contact member projects through the guideway 54 into the arcing chamber 23, as illustrated in Figs. 4 and 5, said end portion abuttin' step 46 in the disengaged condition of the companion contacts, said step serving to limit the movement of the movable contact member in its circuit-open position.

At its end portion 7S, the movable contact member is provided with an integral depending portion 30 which extends through a slot 82 at one end of a thermal-current responsive member S4 which, as here shown, consists of a thermostatic bi-metallic flexible strip which is welded or otherwise secured at said end thereof to a side edge of movable contact member 66. The free end of bi-metallic strip 84 is arranged to releasably engage the latch element 86 at one end of an actuating member or lever 88 pivotally mounted on the end of movable contact member 66 opposite the end which carries the contact 32..

As shown and described in said first mentioned application, and as here shown, the lever 88 is formed in one piece of sheet metal and comprises the laterally spaced opposing walls 90, 90, open between the marginal edges 92, 92 thereof, and partially closed between the opposite marginal edges 94, 94 thereof, by the integral wall 96 which is provided with the aforementioned latch element 86, depending below said opposing walls, and with the longitudinal reinforcing bead 98 offset laterally outwardly thereof. rl`he walls 9d, 9i? are provided with the confronting punched-in, cylindrical projections i), 16), respectively, which are mounted for pivotal movement in a bearing aperture 102 provided in the movable Contact member 66 at the aforementioned opposite end thereof. An insulation bushing 103 is provided in bearing aperture 162 to insulate lever 8S from contact member 66. It will be noted from Figs. 6 and 8, that when the lever ii is mounted on the movable contact member 66, the walls 9i) straddle said movable member. At their free ends,

each wall 90 is provided with an aperture 104. One

end 166 of a resilient link '108 'extends with slight clearance through the aligned apertures 104 (Fig. 6) and the other end of said link is pivotally engaged with the adjacent end of handle 64. A coil compression spring 11i) is operatively interposed between the movable contact member 66 and handle 64 for biasing the movable contact member to its open position. One end of said spring engages a lug 112 carried by handle 64 and the other end of said spring engages a lug 114 integral with the movabie Contact member 66. The mechanism constituted by handle 64, movable contact member 66, thermal strip 64, lever 8S and link 16S is similar to and operates substantially in the same way as corresponding mechanism in United States Patent Re. No. 23,188.

Also shown and described in said first mentioned application and as here shown, the movable Contact member 6 is provided with a generally circular, peripherally interrupted, tapered aperture 116 and a tapered pin 11S for Calibrating the circuit breaker. Said aperture is formed in the marginal edge of said movable contact member the juncture of the narrowed portion 12d thereof, on which lever S8 is pivotally mounted, and the wider body portion 122 thereof. 1t will be understood that as pin 11S is forced into aperture 116, the portion ofthe movable contact member at the right of pin 11S (Figs. 4 and 5) is bent upwardly in its own plane to decrease the amount of overlap of the detent element 86 at the edge 124 of strip 84 so that less deflection of said strip is required to trip the breaker.

It will be understood that member 84 operates to latch the manually operable actuating mechanism S8 to the movable contact member 66 and to unlatch the actuating mechanism from the movable contact member, the unlatching taking place upon deflection of member 84 causing the disengagement of end 124 thereof from the edge of latch element S6 of lever S8 upon the occurrence of an overload or under other abnormal predetermined current conditions in the circuit controlled by the circuit breaker. When member 34 is deflected from engagement with lever 8S, spring 110 is effective to move contact member 66 to its open position, i. e., from the position illustrated in 5 to the position illustrated in Fig. 4. As heretofore mentioned, the step 46 constitutes a stop for the member 66 to limit the opening movement of the latter. v

The thermal element 84 is connected in series with movable contact member 66 and the circuit which is to be controlled by the circuit breaker. For this purpose a flexible metallic conductor or connector 126 is connected to said thermal element, preferably adjacent to the free end 124 thereof, and extends from chamber 54, through an opening 61 in Wall portion 6d, into chamber 22 for connection to the stab contact 24 which makes contact with a power line in the terminal panel assembly of the co-pending application of Thomas M. Cole and myself, identified above.

Load terminal 76 which carries the stationary Contact 30, is positioned in in the casing. As illustrated and described in said firstmentioned application, and as here shown, said terminal comprises an integral conducting strip 136 which is shaped to form the vertically disposed opposing walls 132 and 134, and the horizontally disposed opposing walls 136 and 138 of the terminaLkwhen the casing is mounted in the position illustrated in Figs. 1 through 5. One end portion 146 of said strip extends inwardly beyond wall 134 and carries the stationary contact 30. The inner end of part 140 abuts the shoulder portion 142 of the casing body to position contact Sil in relation to contact 32. The lower end of wall 134 is of reduced width and passes through an opening in wall 138 and is bent under the latter as indicated at 14S. Said end portion 140 is provided with the laterally extending projections 144 which extend into aligned recesses 146 in the confrontingsnrfaces of both casing parts. Portion 143 abuts a stop 154i formed in portion 34 of body part 12 and overlying an extending portion 152 thereof. 1t will be noted that when the cover member 14 is secured to the body part 12, the terminal 76 cannot be removed from the casing, movement in a horizontal plane being prevented by shoulder 142 and stop 150, and movement in a vertical plane being prevented by the arms 144 positioned in the recesses 146, and the underlying projection 152 and the overlying portion 154 of wall portion 38 which abuts the upper surface of strip portion 141). A terminal screw 156 is engaged in a threaded aperture in wall 136 and aperture 15,8 is

formed in wall 132 for Vthe insertion of a lead wire between said terminal screw and the upper surface of wall 138.

As illustrated and described in said first mentioned application, the thermal current-responsive member 84 is preferably operable not only` in response to the heating effect of the current passing therethrough, but is also operable under the control of electro-magnetic means for effecting disengagement of the companion relatively movable contacts 36 and 32, and the arrangement is preferably such that, as here shown, the electro-magnetic means is energized by the current which passes through the said thermal current-responsive member. For this purpose an electro-magnetic member 166 is lixedly se` an open recessed portion 128 formedV cured, preferably by welding, or in other suitable manner, on member 84 near the free end thereof and av companion rigid armature 162 is disposed in spaced confronting relation to electro-magnetic member 160. As shown in Fig. 6, magnetic member 160 straddles member 84 by which it is carried. Said member 160 is formed in one piece of soft sheet steel or other suitable sheet metal and is provided with an end wall, opposed side walls, and with out-turned end portions 164 which are arranged in surface-confronting relation to the adjacent surface of armature 162. As shown in Fig. 7, armature 162 is provided with a slotted portion 166, opposite the free end thereof, which is aligned with slot 82 in member 84. 'Ille armature is secured to the xed end of member 84, preferably by welding, the depending portion 80 of movable member 66 extending through said aligned slots and being riveted to the outer surface of the armature. At its free provided with the out-turned portions 162 operate substantially in the same way as cor espending mechanism in said United States Patent Re. No. 23,188.

In accordance with the present invention, provision is made for preventing arcs, which may be formed upon the disengagement of movable contact 32 from the stationary contact 30, from entering chamber 55, in which the cirmechanism is contained, forcing the arcs into the arcing chamber 28 and through the opening 35 to the exterior of casing 10. Pursuant thereto, there is provided the blow-out means 172. As shown in Figs. 4, 5, 7 and 8, said blow-out means is in the form of a U-shaped member 164 formed as an integral part of the armature 162 opposite the free lend thereof. Said armature, including said member 174, is of magnetizable material and is preferably formed in one (Fig. 4) to also straddle the conpanion stationary contact 30, when said contacts are engaged, as shown in Figs. 5 and 7. As illustrated in Figs. 7 and 8, the blow-out member 174 is dimensioned to tit, with a slight clearance in guideway S4 and is freely movable therein by the movable contact member 66,'4 to and from the positions illustrated in Figs. 4 and 5. It will be noted from Figs. 4 and 5 that member 174 extends from within the mechanism chamber 55 through the passageway 54 and into the arcing chamber 28 to form an arc chute between said chambers.

Referring now to Fig. 13A, the companion contacts 30 and 32 are shown spaced from each other to define an arc-gap 182 therebetween. Assuming a current ow from contact 30 to contact 32 across gap 182, said currentilo'w generating an arc between said contacts, the current will ow through portion 78 of the movable contact'member 66 to and through thermostatic member 84. Said current ow is represented diagrammatically by line 184, the arrow heads 186 indicating the direction of ilow. As is well understood by those skilled in the art, said current flow will polarize said blow-out member 174 whereby to create a magnetic iield in a direction determined by said current flow between the horns 178 of blow-out member 174, and, as illustrated schematically inFig. 13B, .the mag-v netic linesof force or ux 187 or'said'iield .will bein the direction indicated `by the arrow-heads said lines-187.` In addition, a magnetic field is createdv around the lineof current lilow 184 through portion v78, said iield being indi- In- Fig. 13B, portion arrow 192. Consequently, as understood by those skilled in the art, the resultant magnetic field on the side of the wire in the direction of arrow 192 will be increased and the resultant magnetic field in the direction of arrow 194 breaker is reversed, on the line of current flow 184 in Fig. 14A by the arrowheads 186', said blow-out member 174 will be polarized in an opposite direction, whereby the direction of the previously described magnetic tields also reverse. Specifically, the lines of flux 187 between the horns 178 will be in a direction opposite the linx lines 187, and the iiux 188 about wire 190', which indicates a current flow in a direction out of the drawing, will be in a counter-clockwise direction. It will be noted that the flux 188' will oppose those magnetic lines of force 187 lying on the side of wire 190', indicated by the arrow 194', and will be in the same direction as those magnetic lines of force 187' lying on the other side of said wire, as indicated by the arrow 192'. Consequently, the resultant magnetic field in the direction of arrow 192' will be increased and the resultant magnetic field in the direction of arrow 194' will be decreased to provide a resultant magnetic motion or force in the direction of said arrows 194', as illustrated in Figs. 14A and 14B. Since the directions of arrows 194 and 194' is the same, it will be apparent that, regardless of the direction of current flow between the horns 178, the resultant magnetic motion or force is always in the same direction, namely, in the directions of arrows 194 and 194' which direction is transversely of arcing chamber 28 and toward the wall 34 thereof which is provided with the exterior opening 35. Said resultant magnetic motion, being in a direction away from chamber 55 in which the circuit breaker mechamsm is contained, will tend to force or blow the arcs away from said chamber into the arcing chamber and out of the opening 35 to the exterior of the casing. Since the horns 178 are narrowest at the free ends 180 thereof, the density of linx lines 137 will be greatest between said ends thereby resulting in a maximum resultant magnetic motion adjacent the movable contact. 32 in at almaximum, said maximum motion always being at the maximum point of the arc4 since said ends 180 move with the contact 32.

Fig. 9 illustrates a modified form of construction. As there shown, the blow-out member 174' is not integral with the armature 162 but constitutes a separate component. The depending portion of movable contact member 66 passes through slotted portions of the thermostatic element 84 and the armaturer162, as previously lde-- scribed, and through a slot 196 in the bight 176 of metri-f ber 174', the latter being welded, or otherwise suitably secured, to the outer surfaceof the armature.

In the embodiment illustrated in Fig. l0, the magnet and the armature 162 are eliminated, the blow-out member 174 being secured directly to the thermostatic element 84 at the point at movable contact member 66, the depending portion 80 of said latter member, passing through theslot 196 in the blow-ot member, .the same manner as in Fig. 9.-

In the` embodiment illustrated-in Figs. 1l,` and; 12, the blow-out member 174" portion *12 of the casing. As here shown, member 174"- abu'ts the aforementioned step,4 6, being secured to the having a current flow in4 which the latter is secured to the.

isV fixedlysecured to the body' casing by means of the screw 198. It will be noted that member 174" is enlarged so that the free ends 180 thereof straddle the fixed contact 3d, as in the closed condition of the circuit breaker illustrated in Fig. 5, said member 174" operating in the same manner as member 174 and straddling the path of movement of the movable contact 32.

While I have illustrated and described the arc blowout means of my invention in connection with a circuit breaker having a stab contact, it will be understood that it is not limited to use with the specic type of circuit breaker herein described, and that it is adaptable for use in electric devices other than circuit breakers.

While I have shown and described the preferred embodiment of my invention, it will be understood that various changes may be made in the present invention without departing from the underlying idea or principles of the invention within the scope of the appended claims.

Having thus described my invention, Vwhat I claim and desire to secure by Letters Patent, is:

l. ln an electric device, a casing having portions delining an arcing chamber therein, said casing having an opening extending from said chamber to the exterior of the casing, a stationary vcontact disposed in said arcing chamber, a companion contact movable into engagement with and disengagement from said stationary contact, and a blow-out member straddling said contacts in the engaged condition thereof for directing arcs generated between said contacts through said arcing chamber to the exterior of said casing, said blow-out member being secured to said casing and exte Y chamber, said blow-out member being a U-shaped member having a bight provided with upwardly extending horn elements which straddle the path of movement of said companion contact.

2.'ln an automatic circuit breaker, a casing having portions deiining an arcing chamber having an opening extending from said chamber to the exterior of the casing, a stationary contact disposed in said arcing chamber, a movable contact member provided with a companion contact engageable with and disengageable from said stationary contact, means for latching said ding into said arcingA therein, said casing movable contact member in the engaged condition of said contacts and for unlatching said movable member to disengage said contacts at predetermined current conditions in said circuit breaker, said means including an electromagnetic armature carried by said movable contact member, and blow-out means for directing arcs generated between said companion contacts through said arcing chamber to the exterior of said casing, said blow-out means being magnetically polarizable bythe current flow through said breaker and being a portion of said armature extending into said arcing chamber and straddling said companion contacts in the engaged condition thereof, whereby the polarization of said blow-out means is determined by the direction of current iiow through said contacts.

3. In an automatic circuit breaker, a casing having portions defining an arcing chamber therein, said casing having anr opening extending from said chamber. to the exterior of the casing, a stationary contact disposed in said arcing chamber, a 'movable contact member provided with a companion contact engageable with and disen-A gageable from said stationary contact, means for latching said movable contact member in the engagedcondition of s ,aid contacts and for unlatching said movable member to disengage said contacts at predetermined current conditions in said circuit breaker, said means including an electro-magnetic armature carried by said movable contact member, and blow-out means for directing arcs generatedbetween said companion contacts through said arcing chamber to the exterior of said casing, said blow-out-I means being magnetically polarizableY by the current ow through said breaker and being a portion of said armature vextending into said arcing chamber and straddling said companion contacts in the engaged condition thereof, said portion being U-shaped and provided with horn elements extending above said movable contact;

whereby the magnetic polarization of said horn elements is determined by the direction of current ow through said contacts.

4. In an automatic circuit breaker, a casing having portions deiining contiguous chambers therein and a passageway therebetween, one of said Vchambers being'provided with an opening extending through said casing to the exterior thereof, a stationary contact disposed in said one chamber, a movable contact member mounted in the other chamber and having a portion extending through said passageway, said portion being provided with a companion contact engageable with and disengageable from said stationary contact, and a blow-out member secured to said casing and disposed in said passageway, said blow-out member extending into'said one chamber for directing arcs generated in saidv one chamber through the opening therein to the exterior of said casing, said member being provided with spaced horns between which said portion is movable, said horns straddling said stationary contact and the path of movement of said companion contact.

5. In an automatic circuit breaker having relatively movable contacts and an operating mechanism for engaging said contacts with and disengaging them from each other, said mechanism comprising current conducting and current-responsive control means bodily movable with one of said contact members, the combination with said one of said contact members of magnetizable arc blowout means bodily movable therewith and polarizable in a direction determined by the direction of the current flowing in said current-responsive means and positioned in arc 35 blow-out relation to said relatively movable contacts for directing arcs which may be formed, upon disengagement of said contacts, in a direction away from said operating mechanism, said current-responsive means comprising a liexible bi-metallic thermostatic strip for releasably latching said mechanism in the contact-engaged condition of the circuit breaker and said arc blow-out means being in xed relation to said exible strip, and companion magnetic means comprising an integral portion of said blowout means and a part carried by said strip for flexing the latter, upon predetermined current flow in the strip, for unlatching said mechanism to trip the circuit breaker.

6. In an automatic circuit breaker, complementary casing members secured together in housing defining relation, said members having portions which define an arcingy chamber provided with an Yopening to the exterior of the housing, a chamber for the circuit breaker mechanism and a passageway between said chambers, a stationaryl contact disposedl in said arcing chamber, said mechanism including a movable contact member which extends from said mechanism chamber into said arcing chamber and is provided with Va contact which is operable thereby. in said arcing chamber to engage and disengage said stationary contact, and arc-confining chute means in said passageway, said chute means extending between said chambers to protect adjacent portions ot the housing from the arcs, said c hute being formed of magnetic material to constitute a blow-out device for directing arcs generated in said arcingV chamber in a direction away from said mechanism chamber and toward said opening, whereby the arcs are substantially prevented from entering the mechanism chamber.

7. An automatic circuit breaker as defined in claim 6,

further characterized in that said arc-conning chute means substantially fills said passageway and has opposite end portions thereof extending into each of said chambers respectively.

8. In an automatic circuit breaker, complementary casingl members secured together in housing defining relation, said members having portions which define anA arcing chamber provided with an opening to the exterior ofthe housing, a chamberA for the circuit breaker mechanism and a passageway between said chambers, a stationary contact disposed in said arcing chamber, said mechanism including a movable contact member which extends from said mechanism chamber into said arcing chamber and is provided with a contact which is operable thereby in said arcing chamber to engage and disengage said stationary contact, and arc-confining chute means carried by said movable Contact member and disposed thereby in said passageway, said chute means being dimensioned to extend from one of said chambers into the other ot said chambers through said passageway to protect adjacent portions of the housing from the arcs, said chute being formed ot magnetic material to constitute a blowout device for directing arcs generated in said arcing chamber in a direction away from said mechanism chamber and toward said opening, whereby the arcs are substantially prevented from entering the mechanism chamber.

9. An automatic circuit breaker as defined in claim 3, further characterized in that said device is a U-shaped member which straddles said movable Contact member and is provided with spaced tapered horn elements which extend above the movable contact.

l0. An automatic circuit breaker as defined in claim 8, further characterized in that said device is a U-shaped member which straddles said movable contact member and is provided with spaced tapered horn elements which extend above the movable contact, said movable member having a depending marginal portion on which the big'nt of said U-shaped member is mounted.

ll. An automatic circuit breaker as defined in claim 8, further characterized in that said device is a U-shaped member which straddles said movable contact member and is provided with spaced tapered horn elements which extend above the movable contact, said movable member having a depending marginal portion on which the bight of said U-shaped member is mounted, said circuit breaker mechanism including a thermal current control element carried by said depending portion of said movable member.

12. In an automatic circuit breaker, a casing having portions defining an arcing chamber therein, said casing having an opening extending from said chamber to the exterior of the casing, a stationary Contact disposed in said arcing chamber, a movable contact member having a companion contact engageable with and disengageable from said stationary contact, and a blow-out member carried by said movable member, said blow-out member having spaced horn elements which extend therefrom to straddle said movable contact for directing arcs generated between said contacts toward said opening, said movable contact member mounting the movable contact and the blow-out member at opposite portions thereof, said spaced horn elements straddling said opposite portions, said blow'out member being formed of magnetizable material and said horns being polarizable in a direction determined by the direction of current ilow between said opposite portions of said movable Contact member, means for latching said movable Contact member in the engaged condition of said contacts, and means for unlatching said movable Contact member to disengage said contacts at predetermined current conditions in said circuit breaker, said latching means including a flexible element, and said uulatching means being a portion of said blow-out member extending therefrom in spaced relation to said exible element, said extending portion of said blow-out member being magnetized by the current ow through the circuit breaker to constitute an electro-magnetic armature to which said flexible element is attracted at the occurrence of said predetermined current condition for unlatching the movable Contact member.

References Cited in the le of this patent UNITED STATES PATENTS 

